The present invention relates generally to electric motors, generators, and regenerative motors. The term regenerative motor is used herein to refer to a device that may be operated as either an electric motor or a generator.
More specifically, the invention relates to an electric motor, generator, or regenerative motor including a stator arrangement which itself includes an electromagnet assembly having an amorphous metal magnetic core made up of a plurality of individually formed amorphous metal core pieces. The present invention also provides a control arrangement that is able to variably control the activation and deactivation of an electromagnet using any combination of a plurality of activation and deactivation parameters in order to control the speed, efficiency, power, and torque of the device.
The electric motor and generator industry is continuously searching for ways to provide motors and generators with increased efficiency and power density. For some time now, it has been believed that motors and generators constructed using permanent super magnet rotors (for example cobalt rare earth magnets and Neodymium-Iron-Boron magnets) and stators including electromagnets with amorphous metal magnetic cores have the potential to provide substantially higher efficiencies and power densities compared to conventional motors and generators. Also, because amorphous metal cores are able to respond to changes in a magnetic field much more quickly than conventional ferrous core materials, amorphous metal magnetic cores have the potential to allow much faster field switching within motors and generators, and therefore allow much higher speed and better controlled motors and generators than conventional ferrous cores. However, to date it has proved very difficult to provide an easily manufacturable motor or generator which includes amorphous metal magnetic cores.
Amorphous metal is typically supplied in a thin continuous ribbon having a uniform ribbon width. However, amorphous metal is a very hard material making it very difficult to cut or form easily, and once annealed to achieve peak magnetic properties, becomes very brittle. This makes it difficult and expensive to use the conventional approach to constructing a magnetic core. This conventional approach typically involves cutting individual core layers having a desired shape from a sheet of core material and laminating the layers together to form a desired overall magnetic core shape. The brittleness of amorphous metal also causes concern for the durability of a motor or generator which utilizes amorphous metal magnetic cores. Magnetic cores are subject to extremely high magnetic forces which change at very high frequencies. These magnetic forces are capable of placing considerable stresses on the core material which may damage an amorphous metal magnetic core.
Another problem with amorphous metal magnetic cores is that the magnetic permeability of amorphous metal material is reduced when it is subjected to physical stresses. This reduced permeability may be considerable depending upon the intensity of the stresses on the amorphous metal material. As an amorphous metal magnetic core is subjected to stresses, the efficiency at which the core directs or focuses magnetic flux is reduced resulting in higher magnetic losses, reduced efficiency, increased heat production, and reduced power. This phenomenon is referred to as magnetostriction and may be caused by stresses resulting from magnetic forces during the operation of the motor or generator, mechanical stresses resulting from mechanical clamping or otherwise fixing the magnetic core in place, or internal stresses caused by the thermal expansion and/or expansion due to magnetic saturation of the amorphous metal material.
Conventional magnetic cores are formed by laminating successive layers of core material together to form the overall core. However, as mentioned above, amorphous metal is difficult to cut or form easily. Therefore, in the past, amorphous metal cores have often been formed by rolling an amorphous metal ribbon into a coil with each successive layer of the material being laminated to the previous layer using an adhesive such as an epoxy. When in use in an electric motor or generator, this laminated construction restricts the thermal and magnetic saturation expansion of the coil of amorphous metal material and results in high internal stresses. These stresses cause magnetostriction that reduces the efficiency of the motor or generator as described above. Also, this construction places a layer of adhesive between each coil of the core. Since amorphous metal material is typically provided as a very thin ribbon, for example only a couple of mils thick, a significant percentage of the volume of the core ends up being adhesive material. This volume of adhesive reduces the overall density of the amorphous metal material within the laminated core, and therefore, undesirably reduces the efficiency of the core to focus or direct the magnetic flux for a given volume of overall core material.
The present invention provides a method and arrangement for minimizing the stresses on an amorphous metal magnetic core in an electric motor, generator, or regenerative motor. This method and arrangement eliminates the need for laminating the various layers of the amorphous metal thereby reducing the internal stresses on the material and increasing the density of the amorphous material within the overall core. Also, in order to take advantage of the high speed switching capabilities of the amorphous metal magnetic core material, the present invention provides control methods and arrangements that are able to variably control the activation and deactivation of the electromagnet of an electric motor, generator, or regenerative motor device including an amorphous metal magnetic core by using a combination of a plurality of different activation and deactivation parameters in order to control the speed, efficiency, torque, and power of the device.
As will be described in more detail hereinafter, a device such as an electric motor, an electric generator, or a regenerative electric motor is disclosed herein. The device includes a rotor arrangement, at least one stator arrangement, and a device housing for supporting the rotor arrangement and the stator arrangement in the predetermined positions relative to one another. The device housing also supports the rotor arrangement for rotation along a predetermined rotational path about a given rotor axis. The stator arrangement has at least one energizable electromagnet assembly including an overall amorphous metal magnetic core and an electric coil array which together define at least one magnetic pole piece. The overall amorphous metal magnetic core is made up of a plurality of individually formed amorphous metal core pieces. The stator arrangement also includes a dielectric electromagnet housing for supporting the electromagnet assembly such that the magnetic pole pieces are positioned adjacent the rotational path of the rotor arrangement. The dielectric electromagnet housing has core piece openings formed into the electromagnet housing for holding the individually formed amorphous metal core pieces in positions adjacent to one another so as to form the overall amorphous metal magnetic core.
In one preferred embodiment, the rotor arrangement has at least one rotor magnet with north and south poles and the rotor arrangement has an arrangement for supporting the rotor magnet for rotation about a given rotor axis such that at least one of the magnet""s poles is accessible along a predetermined rotational path about the given rotor axis. In a preferred embodiment, the rotor magnet is a super magnet.
In some embodiments, the individually formed amorphous metal core pieces are amorphous metal windings formed from a continuous ribbon of amorphous metal. Preferably, the continuous ribbon of amorphous metal has a substantially constant ribbon width. The individually formed amorphous metal core pieces may have a variety of cross-sectional shapes including a circle, an oval, an egg shape, a toroidal ring, a triangle having rounded corners, and a trapezoid having rounded corners. Alternatively, the individually formed amorphous metal core pieces may be formed from individual strips of amorphous metal material stacked in an associated core piece opening of a core piece housing. Also, in some embodiments, any voids in the core piece openings of the electromagnet housing holding the amorphous metal core pieces are filled with a dielectric oil. Additionally, the amorphous metal core pieces may be oil impregnated.
In one embodiment, the stator arrangement includes a plurality of electromagnet assemblies, each having a plurality of pole pieces. Each of the pole pieces is an individually formed amorphous metal core piece. Furthermore, at least one of the individually formed amorphous metal core pieces is a toroidal ring forming an electromagnetic yoke magnetically coupling each of the pole pieces to one another. The toroidal ring electromagnetic yoke includes an annular or other such continuous surface defined by one continuous edge of the continuous ribbon of amorphous metal after the ribbon of amorphous metal has been wound about itself. Each of the pole pieces of the electromagnet assembly has a first end (defined by one continuous edge of the ribbon) positioned adjacent the predetermined rotational path of the rotor magnet. Also, each of the pole pieces of the electromagnet assembly has a second end (defined by the other continuous edge of the ribbon) positioned adjacent the annular surface of the toroidal ring electromagnetic yoke.
In another embodiment, the electromagnet of the stator arrangement includes a generally U-shaped overall amorphous metal magnetic core having two pole pieces. The two pole pieces are each individually formed amorphous metal core pieces. An additional individually formed amorphous metal core piece forms an electromagnetic yoke magnetically coupling the two pole pieces to one another such that the core pieces together define the U-shaped overall core.
In still another embodiment, the arrangement supporting the rotor magnet supports the rotor magnet such that both the north and the south poles of the rotor magnet are accessible along different predetermined rotational paths about the given rotor axis. The electromagnet of the stator arrangement includes a generally C-shaped overall amorphous metal magnetic core having two pole pieces with each of the pole pieces positioned adjacent to a corresponding one of the predetermined rotational paths of the north and south poles of the rotor magnet. The overall magnetic core of the electromagnet assembly is a generally C-shaped overall amorphous metal magnetic core defining the two pole pieces such that each of the pole pieces is positioned adjacent to a corresponding one of the different predetermined rotational paths. The two pole pieces are each individually formed amorphous metal core pieces. Additional individually formed amorphous metal core pieces form an electromagnetic yoke magnetically coupling the two pole pieces to one another such that the core pieces together define the C-shaped overall core.
A method of making an amorphous metal magnetic core for an electromagnet of a device such as an electric motor, an electric generator, or a regenerative electric motor is also disclosed herein. The method includes the step of forming a plurality of individually formed amorphous metal core pieces, each having a desired core piece shape. A dielectric magnetic core housing including magnetic core piece openings that define the desired overall magnetic core shape is provided. The plurality of individually formed amorphous metal core pieces are assembled into the core piece openings of the dielectric magnetic core housing such that the dielectric core housing holds the core pieces adjacent to one another so as to form the desired overall magnetic core shape. In a preferred method, each core piece is wound into its final shape from a continuous ribbon of amorphous metal.
In accordance with another aspect of the present invention, a method and arrangement for controlling the rotational speed and input/output power and torque of a device such as an electric motor, an electric generator, or a regenerative electric motor is disclosed herein. The device includes a rotor supported for rotation along a predetermined rotor path about a given rotor axis. Preferably, the rotor includes at least one permanent super magnet. The device also includes a stator having a plurality of dynamically activatable and deactivatable electromagnet assemblies (also referred to herein merely as electromagnets) with amorphous metal magnetic cores. The electromagnets are spaced apart from one another adjacent to the predetermined rotor path such that movement of a particular point on the rotor (rotor point) from a given point adjacent one electromagnet (stator point) to a given point adjacent the next successive electromagnet (stator point) defines one duty cycle. A position detector arrangement determines the position and rotational speed of the rotor relative to the stator at any given time in a duty cycle and produces corresponding signals. A controller responsive to the signals controls the activation and deactivation of the electromagnets of the stator using predetermined device control settings such that, for each duty cycle, the controller is able to control any combination of a plurality of activation and deactivation parameters in order to control the speed, efficiency, and input/output power and torque of the device.
In a preferred embodiment, the activation and deactivation parameters include (i) the duty cycle activation time which is the continuous duration of time in which the electromagnet of the stator is activated (with either one polarity or the other) for each duty cycle, (ii) the start/stop points of the duty cycle activation time which are the times at which the duty cycle activation time starts and stops during the duty cycle relative to the rotational position of the rotor as it moves through the duty cycle from stator point to the next adjacent stator point, and (iii) the modulation of the duty cycle activation time which is the pulse width modulating of the electromagnet by activating and deactivating the electromagnet during what would otherwise be the continuous duty cycle activation time.
In another embodiment, the position detector arrangement includes an encoder disk supported for rotation with the rotor and also includes an array of optical sensors arranged in close proximity to the encoder disk. The encoder disk has a plurality of concentric tracks with spaced apart position indicating openings which are actually through-holes in the disk. Each of the optical sensors corresponds to and is optically aligned with an associated one of the concentric tracks such that each sensor is able to detect the presence of the position indicating openings defining its associated concentric track so as to be able to detect the position of the rotor relative to the stator. Preferably these openings are sized and positioned to represent a digital byte of rotor positional information with each track contributing one bit of the overall digital byte. In this way, during startup of the motor/generator device, the position of the rotor can be precisely determined.
In still another embodiment, the controller further includes a counter arrangement capable of counting in increments of time which allow each duty cycle to be divided into a multiplicity of time periods which the controller uses to control when to activate and deactivate the electromagnet.
In accordance with another aspect of the present invention, a method and arrangement for conditioning the electrical output of an electric generator driven by a input drive device is disclosed. The generator includes a stator assembly having at least one dynamically activatable and deactivatable stator coil and a rotor assembly. A position detector arrangement determines the position and rotational speed of the rotor assembly relative to the stator assembly at any given time and produces corresponding signals. A controller responsive to the signals variably controls the activation and deactivation of the stator coil such that the electrical output of the generator is conditioned to a desired electrical output without requiring the use of additional electrical power conditioning devices. In one embodiment, the input drive device is a wind mill. Furthermore, the controller may use a portion of the electrical power generated by the generator to drive the generator as an electric motor. The generator may be driven as an electric motor in a way which reduces the amount of resistance the generator places on the input drive device or in a way which increases the amount of resistance the generator places on the input drive device.